Sibudjing Kawi

A new class of hybrid mesoporous materials with functionalized organic monolayers for selective adsorption of heavy metal ions

Thiol- and amino-functionalized SBA-15 silicas with uniform mesoporosities were prepared and employed for removing heavy metal ions from waste water; the thiolated SBA-15 adsorbent exhibited a higher complexation affinity for Hg2+, while the other metal ions (Cu2+, Zn2+, Cr3+ and Ni2+) showed exceptional binding ability with its aminated analogue.

Relationships between sensitivity, catalytic activity, and surface areas of SnO2 gas sensors

SnO2 having different surface areas were synthesized using a surfactant-templating synthetic method. The effects of surface areas of the obtained SnO2 on their gas sensing and catalytic properties were investigated. Interestingly, a linear relationship was found between the surface areas of SnO2 and their gas sensitivities to H2 and CO. Furthermore, a linear relationship was observed between the surface areas and the catalytic activities of SnO2 in the oxidation of H2 and CO. Based on the fact that the mechanisms for catalytic reactions and gas-sensing processes both involve surface adsorption and reaction between surface-adsorbed oxygen species and surrounding gases (H2 or CO), the relationship between these two mechanisms occurring on SnO2 surfaces is discussed.

Activated carbon derived from carbon residue from biomass gasification and its application for dye adsorption: Kinetics, isotherms and thermodynamic studies

In this work, activated carbon (AC) as an effective and low-cost adsorbent was successfully prepared from carbon residue (or char, one of the by-products from woody biomass gasification) via physical activation. The surface area of char was significantly increased from 172.24 to 776.46m(2)/g after steam activation at 900°C. The obtained activated carbons were then employed for the adsorption of dye (Rhodamine B) and it was found that activated carbon obtained from steam activation exhibited the highest adsorption capability, which is mainly attributed to the higher surface area and the abundance of hydroxyl (-OH) and carboxyl (-COOH) groups on the activated carbon surface. Moreover, it was also found that the adsorption capability significantly increased under the basic condition, which can be attributed to the increased electrostatic interaction between the deprotonated (negatively charged) activated carbon and dye molecules. Furthermore, the equilibrium data were fitted into different adsorption isotherms and found to fit well with Langmuir model (indicating that dye molecules form monolayer coverage on activated carbon) with a maximum monolayer adsorption capability of 189.83mg/g, whereas the adsorption kinetics followed the pseudo-second-order kinetics.

High-surface-area SnO2 : a novel semiconductor-oxide gas sensor

Abstract High surface area SnO 2 sensor materials were systematically synthesized by a surfactant incorporating method. After calcination at 723 K, a high BET surface area of 156.8 m 2 /g was obtained. The sensing properties of the high surface area SnO 2 material were studied using H 2 as the probing gas. It is found that a linear relationship exists between sensor surface area and its sensitivity to H 2 .

MCM-41 MODIFIED SNO2 GAS SENSORS : SENSITIVITY AND SELECTIVITY PROPERTIES

Abstract MCM-41 modified SnO 2 (SnO 2 /MCM-41) gas sensors were prepared by mechanically mixing SnO 2 with MCM-41 (which is a novel high-surface-area mesoporous material) followed with thermal treatment in air at 700°C. H 2 , CO and CH 4 were selected as probing gases to characterize the sensing properties of these sensors. Compared with those of the pure SnO 2 sensor, SnO 2 /MCM-41 sensors showed enhanced sensitivities and selectivity to H 2 . It was found that the SnO 2 /MCM-41 sensor having SnO 2 content of SnO 2 /MCM-41=0.7 (weight ratio) possessed the highest H 2 sensitivity. The sensitivities to CO and CH 4 were also found to be improved on the SnO 2 /MCM-41 sensors at much higher temperature ranges. The effect of SnO 2 content on the sensitivity and selectivity to CO and CH 4 were also investigated. The mechanistic aspect due to the enhancement of the sensitivity and selectivity of SnO 2 /MCM-41 gas sensors to H 2 is briefly discussed.

A highly dispersed and anti-coking Ni–La2O3/SiO2 catalyst for syngas production from dry carbon dioxide reforming of methane

Syngas production from dry carbon dioxide reforming of methane was studied on a Ni/SiO2 doped with La2O3 catalyst prepared via an in situ self-assembled core–shell precursor route. Highly dispersed nickel of particle size <3.0 nm on the Ni–La2O3/SiO2 catalyst was successfully achieved. The addition of La2O3 enhanced the interaction between NiO and the silica support to form a more stable nickel silicate. The resulting Ni–La2O3/SiO2 catalyst showed excellent catalytic activity and stability without any coking behaviour even after 100 hours of reaction on stream. In contrast, the Ni–La2O3/SiO2 catalyst prepared using a conventional incipient wetness impregnation method exhibited poor catalytic activity and a high coke formation rate.

Solubility of cholesterol and its esters in supercritical carbon dioxide with and without cosolvents

Abstract The solubilities of cholesterol and its esters—cholesteryl acetate, cholesteryl butyrate and cholesteryl benzoate—in supercritical carbon dioxide were measured using a dynamic flow method. We also examined the effect of a polar cosolvent, namely methanol or acetone, on the solubility of these compounds in supercritical carbon dioxide and found that the solubilities of these compounds are enhanced several fold depending on the pressure of the system. The solubility data were correlated using the Peng–Robinson equation of state (PR EOS) and density-based correlations. Model parameters for the systems studied are obtained through data regression.

Progress in Synthesis of Highly Active and Stable Nickel‐Based Catalysts for Carbon Dioxide Reforming of Methane

In recent decades, rising anthropogenic greenhouse gas emissions (mainly CO2 and CH4 ) have increased alarm due to escalating effects of global warming. The dry carbon dioxide reforming of methane (DRM) reaction is a sustainable way to utilize these notorious greenhouse gases. This paper presents a review of recent progress in the development of nickel-based catalysts for the DRM reaction. The enviable low cost and wide availability of nickel compared with noble metals is the main reason for persistent research efforts in optimizing the synthesis of nickel-based catalysts. Important catalyst features for the rational design of a coke-resistant nickel-based nanocatalyst for the DRM reaction are also discussed. In addition, several innovative developments based on salient features for the stabilization of nickel nanocatalysts through various means (which include functionalization with precursors, synthesis by plasma treatment, stabilization/confinement on mesoporous/microporous/carbon supports, and the formation of metal oxides) are highlighted. The final part of this review covers major issues and proposed improvement strategies pertaining to the rational design of nickel-based catalysts with high activity and stability for the DRM reaction.

Simultaneous Tuning Porosity and Basicity of Nickel@Nickel–Magnesium Phyllosilicate Core–Shell Catalysts for CO2 Reforming of CH4

Ni@Ni-Mgphy (Ni-Mgphy = Ni-Mg phyllosilicate) core-shell catalysts were designed by hydrothermally treating Ni@SiO2 nanoparticles with magnesium nitrate salt. The porosity and basicity of the catalysts were easily tuned by forming Ni-Mgphy shell using Ni originating from Ni@SiO2 during the hydrothermal treatment process and Mg(NO3)2 as the Ni and Mg sources, respectively. Among Ni@Ni-Mgphy core-shell catalysts synthesized under different hydrothermal durations, the catalyst treated for 10 h achieved the best catalytic performance for CO2 reforming of CH4 reaction with stable CO2 and CH4 conversions of around 81% and 78%, respectively, within 95 h reaction duration at 700 °C. The high Ni accessibility, strong basicity, and high structural stability for Ni@Ni-Mgphy core-shell catalyst with 10 h treatment time accounted for its superb catalytic performance. This method to simultaneously tune the porosity and basicity of Ni@SiO2 core-shell nanoparticles demonstrates a general way to modify the properties of other silica based core-shell nanoparticles through treating them with different metal salts.

Synthesis, characterization and sensing application of novel semiconductor oxides.

Mesoporous SnO(2) with high surface areas were synthesized using a cationic surfactant (N-cetyl-N,N,N-trimethylammonium bromide) as a synthetic template. Acidity of the starting synthesis slurry was used as one of the controlling parameters for the synthesis. After the SnO(2) was synthesized at pH 7.15, it was calcined at 723 K for 10 h in air. It had a BET surface area of 156.8 m(2) g(-1) with a pore diameter of 38.4 A. Infrared spectroscopy (FTIR) and thermal analysis techniques (thermogravimetry and differential thermal analysis) showed that the surfactant was incorporated in the mesopores of SnO(2) and calcination in air at 673-723 K was needed to remove the surfactant completely from the mesopores. The effects of SnO(2) surface area on its gas sensing properties were also investigated. It was observed that SnO(2) with higher surface areas had much higher sensitivities to hydrogen at 573 K.